Thermal Decomposition of Thallium(I) Bis-oxalatodiaquaindate(III) Monohydrate

Thallium(I) bis-oxalatodiaquaindate(III) monohydrate was obtained by precipitation of indium(III) withoxalic acid from slightly acidic solution in the presence of thallium(I). The complex was subjected to chemical analysis. The thermal decomposition behavior of the complex was studied using TG, DTA and DTG techniques. The solid complex salt and the intermediate product of its thermal decomposition were characterized using IR absorption and X-ray diffraction spectra. Based on data from these physicochemical investigations the structural formula of the complex was proposed as Tl[In (C₂O₄)₂ (H₂O)₂]⋅H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.     

Solid state decomposition studies on metal salicylates. Thermal decomposition of some lanthanide salicylato complexes

The thermal stability and mechanism of thermal decomposition in air of the four lanthanide complexes of 2-hydroxybenzoic acid have been studied by TG, DSC, IR and MS techniques. An analysis of the prepared compounds show that Pr(III), Nd(III) and Tb(III) form anhydrous salicylato (Hsal)⁻ complexes while the corresponding holmium compound contains four water molecules. The TG curves show two (praseodymium, terbium), three (neodymium) or four (holmium) main stages of thermal decomposition. The most unstable among the complexes studied is Ho(Hsal)₃·4H₂O which releases four water molecules in an endothermic dehydration step. Ligand molecules decompose mainly in two stages of which the first is endothermic and is attributed to the release of the ligand acid and the second is a strongly exothermic decarboxylation process. The final decomposition product is the corresponding lanthanide(III) oxide, except in the case of terbium which decomposes to Tb₄O₇.     

Correlation of thermal and spectral properties of chromium(III) picolinate complex and kinetic study of its thermal degradation

Chromium(III) picolinate complex, namely [Cr(pic)₃]·H₂O, was prepared and characterized by the methods of the elemental analysis, infrared spectroscopy, X-ray diffraction, and thermal analysis (TG/DTG, DTA). The correlation of the thermal and spectral properties of the complex with its structure is discussed in the study. The correlation of the spectral data with the structure leads to the accord, and coherence was found between thermal properties and structure of the complex for both steps of the thermal decomposition (dehydration and pyrolysis of organic ligand). Activation parameters were evaluated using the theory of absolute reaction rate.     

Synthesis and characterization of some Cr(III), Fe(III) and Zr(IV) compounds with substituted o-hydroxy benzophenone

This work presents our data concerning the synthesis and characterization of some Cr(III), Fe(III) and Zr(IV) complexes with substituted (2-hydroxy-4-methoxy-phenyl)-phenyl-methanone - C₁₄H₁₂O₃, denoted by (L1). The synthesis of these complex compounds was performed using melted urea as reaction medium. The obtained complexes have been studied by chemical analysis, IR spectroscopy, X-ray diffraction and thermogravimetric analysis. Based on the data resulting from the thermal behaviour of the studied complex compounds, the kinetic parameters of the thermal decomposition reactions have been determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mössbauer study of the thermal decomposition of alkali tris(oxalato)ferrates(III)

The thermal decomposition of alkali (Li,Na,K,Cs,NH₄) tris(oxalato)ferrates(III) has been studied at different temperatures up to 700°C using Mössbauer, infrared spectroscopy, and thermogravimetric techniques. The formation of different intermediates has been observed during thermal decomposition. The decomposition in these complexes starts at different temperatures, i.e., at 200°C in the case of lithium, cesium, and ammonium ferrate(III), 250°C in the case of sodium, and 270°C in the case of potassium tris(oxalato)ferrate(III). The intermediates, i.e., Fe¹¹C₂O₄, K₆Fe¹¹₂(ox)₅. and Cs₂Fe¹¹ (ox)₂(H₂O)₂, are formed during thermal decomposition of lithium, potassium, and cesium tris(oxalato)ferrates(III), respectively. In the case of sodium and ammonium tris(oxalato)ferrates(III), the decomposition occurs without reduction to the iron(II) state and leads directly to α-Fe₂O₃.     

Thermal decomposition of some metal-organic precursors

In this paper we present a study on the synthesis of Fe(III) oxide, by thermal decomposition of some complex combinations of Fe(III) with carboxylate type ligands, obtained in the redox reaction between some polyols (ethylene glycol (EG), 1,2-propane diol (1,2PG), 1,3-propane diol (1,3PG) and glycerol (GL)) and NO₃ ^– ions (from ferric nitrate). Fe₂O₃ was obtained by thermal decomposition of the synthesized metal-organic precursors at low temperatures. γ-Fe₂O₃ was obtained as nanoparticles at 300°C, while at higher temperatures α-Fe₂O₃ starts to crystallize and becomes single phase at ~500°C. The formation of the metal-organic precursors and their thermal decomposition were studied by thermal analysis and FTIR spectroscopy.     

Thermal properties of thiocyanatothiocarbamidobismuthates(III) with alkaline elements

The thermal decomposition of complex salts of thiocyanatothiocarbamidobismuthates(III), having the general formula Me[Bi(SCN)₄(TM)₂] where Me = Li, Na, K, Rb, Cs, NH₄ and TM = thiourea, was studied. On the basis of the results of derivatographic studies and chemical analysis, both infrared spectrophotometric and diffractometric, the compositions of the intermediate and final products obtained during the thermal decomposition of those salts were established. On the strength of the experimental data obtained (without analyzing the gaseous products), the most probable overall equation was established of the decomposition reaction of thiocyanatothiocarbamidobismuthates(III) in air at a temperature of 480°C.     

Thermoanalytical investigations of 4-methylpiperazine-1-carbodithioic acid ligand and its iron(III), cobalt(II), copper(II) and zinc(II) complexes

The thermal decomposition studies on 4-methylpiperazine-1-carbodithioic acid ligand (4-MPipzcdtH) and its complexes, viz. [M(4-MPipzcdtH)_n](ClO4)_n (M=Fe(III) when n=3; M=Co(II), Cu(II) when n=2) and [Zn(4-MPipzcdtH)₂]Cl₂ have been carried out using non-isothermal techniques (TG and DTA). Initial decomposition temperatures (IDT), indicate that thermal stability is influenced by the change of central metal ion. Free acid ligand exhibits single stage decomposition with a sharp DTA endotherm. Complexes, [M(4-MPipzcdtH)_n](ClO₄)_n undergo single stage decomposition with detonation and give rise to very sharp exothermic DTA curves while the complex [Zn(4-MPipzcdtH)₂]Cl₂ shows three-stage decomposition patterns. The kinetic and thermodynamic parameters, viz. the energy of activation E, the frequency factor A, entropy of activation S and specific rate constant k, etc. have been evaluated from TG data using Coats and Redfern equation. Based upon the results of the differential thermal analysis study, the [M(4-MPipzcdtH)_n](ClO₄)_n complexes have been found to possess characteristic of high energy materials.     

A new method of synthesis of BiFeO<Subscript>3</Subscript> prepared by thermal decomposition of Bi[Fe(CN)<Subscript>6</Subscript>]·4H<Subscript>2</Subscript>O

In order to investigate the formation of the multiferroic BiFeO₃, the thermal decomposition of the inorganic complex Bismuth hexacyanoferrate (III) tetrahydrate, Bi[Fe(CN)₆]·4H₂O has been studied. The starting material and the decomposition products were characterized by IR spectroscopy, thermal analysis, laboratory powder X-ray diffraction, and microscopic electron scanning. The crystal structures of these compounds were refined by Rietveld analysis. BiFeO₃ were synthesized by the decomposition thermal method at temperature as low as 600 °C. There is a clear dependence of the type and amount of impurities that are present in the samples with the time and temperature of preparation.     

Research of thermal decomposition of hydrated methanesulfonates

Hydrated methanesulfonates Ln(CH₃SO₃)₃·nH₂O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH₃SO₃)₂·nH₂O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Heterogeneous reactions of solid nickel(II) complexes XXIV

The Stoichiometry of thermal decomposition was studied for the following compounds: Ni(NCS)₂(pip)₄ (I), (pip=piperidine), Ni(NCS)₂(pip)₂py·H₂O (II), (py=piridine), Ni(NCS)₂(4-Mepip)₃ (III), Ni(NCS)₂(3-Mepip)₃ (IV) and Ni(NCS)₂(3.5-Me₂pip)₃ (V). In complexes I, II, III and IV the loss of the volatile ligands (on the TG curve to 300 °C) occurs in three steps and in complex V in two steps. The loss of the last molecules of volatile ligands is accompanied by the decomposition of NCS groups. Spectral data and magnetic moment values for the initial complexes I and II (together with the defined intermediates) indicated pseudooctahedral configuration while pentacoordination for complexes III, IV and V. Structural changes of the complexes studied in thermal decomposition reactions are discussed.     

Lanthanide complexes of 3-methoxy-salicylaldehyde

The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd, Gd, Dy, Er) with 3-methoxy-salicylaldehyde(3-OCH₃-saloH), afforded neutral complexes of the general formula [Ln(3-OCH₃-salo)₃], which were characterized by means of elemental analysis, FT-IR spectra, TG-DTA curves, and magnetic measurements. The released products, due to the thermal decomposition were analyzed by on-line coupling MS spectrometer to the thermobalance in argon, allowed to prove the proposed decomposition stages. In order to confirm the stability scale provided on the basis of the onset decomposition temperature, a kinetic analysis of the three decomposition stages was made using the Kissinger equation, while the complex nature of the decomposition kinetics was revealed by the isoconvertional Ozawa–Flynn–Wall method.     

Thermal decomposition of potassium bis -oxalatodiaqua-indate(III) monohydrate

Indium (III) is precipitated with oxalic acid in the presence of potassium nitrate maintaining an overall concentration of 0·125 M in HNO₃. Chemical analysis of the complex salt obtained indicates the formula, K[In(C₂O₄)₂]·3H₂O. Thermal decomposition studies show that the compound decomposes first to the anhydrous potassium indium oxalate and then to the final mixture of the oxides through formation of potassium carbonate and indium (III) oxide as intermediates. Isothermal study, X-ray diffraction pattern and IR spectral data support the proposed thermal decomposition mechanism.     

Thermal decomposition of hydrotalcite with hexacyanoferrate(II) and hexacyanoferrate(III) anions in the interlayer

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. The thermal decomposition of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer has been studied using controlled rate thermal analysis technology. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 10.9 and 11.1 Å which compares with a d-spacing of 7.9 and 7.98 Å for the hydrotalcite with carbonate or sulphate in the interlayer. Calculations show dehydration with a total loss of 7 moles of water proving the formula of hexacyanoferrate(II) intercalated hydrotalcite is Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.5·7H₂O and 9.0 moles for the hexacyanoferrate(III) intercalated hydrotalcite with the formula of Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.66·9H₂O. CRTA technology indicates the partial collapse of the dehydrated mineral. Dehydroxylation combined with CN unit loss occurs in two isothermal stages at 377 and 390°C for the hexacyanoferrate(III) and in a single isothermal process at 374°C for the hexacyanoferrate(III) hydrotalcite.     

Studies on the thermal decomposition of alkali metal thiosulphatobismuthates(III)

The thermal decomposition of thiosulphatobismuthates(III) of alkali metals was investigated. The general formulae of the thiosulphatobismuthates are M₃[Bi(S₂O₃)₃]·H₂O where M = Na, K, Rb or Cs, and M₂Na[Bi(S₂O₃)₃]·H₂O where M = K or Cs.Typical thermal curves for thiosulphatobismuthates(III) and the results obtained in thermal, X-ray, chemical and spectrophotometrical analyses of the decomposition products are shown. The results were used to determine three stages of the thermal decomposition. At the first stage, at about 200°C, hydrated compounds are dehydrated. At the second stage, above 200°C, there is a rapid decrease in mass which is caused by evolving sulphur dioxide; bismuth sulphide and an intermediate decomposition product are formed. At about 320°C the thermal decomposition products are bismuth sulphide and alkali metal sulphate.     

Preparation of single-phase α-Fe(III) oxide nanoparticles by thermal decomposition. Influence of the precursor on properties

In this research, we present an experimental procedure to prepare single-phase α-Fe(III) oxide nanoparticles by thermal decomposition of five different precursors including: iron(III) citrate; Fe(C₆H₅O₇), iron(III) acetylacetonate; Fe(C₅H₇O₂)₃, and iron(III) oxalate; Fe(C₂O₄)₃, iron(III) acetate; Fe(C₂H₃O₂)₃, and the thermal curves obtained were analyzed. The influence of the thermal decomposition of precursors on the formation α-Fe₂O₃ was studied by differential thermal gravimetry and thermogravimetry. The synthesized powders were characterized by using X-ray diffraction and scanning electron microscopy. High quality iron oxide nanoparticles with narrow size distribution and average particle size between ca. 2 and 30 nm have been obtained. It was found that the iron precursors affect the temperatures of the pure α-Fe₂O₃ nanoparticle formation with different diameters; iron(III) citrate (29 nm), iron(III) acetylacetonate (37 nm), and iron(III) oxalate (24 nm).     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Mixed ligand complexes of nickel(II) and cerium(III) ions with 4-(-3-methoxy-4-hydroxybenzylideneamino)-1, 3-dimethyl-2,6-pyrimidine-dione and some nitrogen/oxygen donor ligands

Mononuclear mixed ligand complexes of Ni(II) and Ce(III) with 4-(-3-methoxy-4-hydroxybenzylideneamino)-1,3-dimethyl-2,6-pyrimidine-dione, 2-aminopyridine and 8-hydroxyquinoline have been prepared. The elemental analysis, molar conductance, spectral (IR, mass and solid reflectance), magnetic moment measurements and thermal study were utilized to investigate the coordination behavior. All metal complexes have metal-to-ligand ratios of 1:1:1 and the modes of bonding are consistent with N- and O-donation suggesting monomeric octahedral and square planar structures. The thermal behavior of these complexes was investigated and the thermal decomposition pathways postulated. The activation thermodynamic parameters, E*, ΔH*, ΔS* and ΔG* for the different thermal decomposition steps of the complexes were calculated using the Coats-Redfern equation. Antibacterial and antifungal properties of the metal complexes have also been examined against Staphylococcus aureus (ATCC 25923), Streptococcus pyogenes (ATCC 19615), Pseudomonas fluorescens (S 97), Pseudomonas phaseolicola (GSPB 2828), Fusarium oxysporum and Aspergillus fumigatus. The highest antimicrobial activity was observed for the Ce(III) complex, [CeL(8-Oqu)(NO₃)₂]·1½H₂O.     

Mass spectra of methylsubstituted monosila- and monogermacyclobutanes, 1,2- disila- and 1,2-digermacyclopentanes. Some correlations with thermal decomposition

The mass spectra of 1,1-dimethyl-1-silacyclobutane (I—as reported by Cherniak et al.),⁶, 1,1-dimethyl-1-germacyclobutane (II), 1,1,2,2-tetramethyl-1,2-disilacyclopentane (III) and 1,1,2,2-tetramethyl-1,2-digermacyclopentane (IV) are compared and some correlations between electron-impact fragmentation and thermal decomposition are derived. The mass spectra of the germanium compounds with respect to the silicone compounds are enriched by light fragment ions and exhibit lower intensities of odd-electron ions. The composition of some ions and apparently of neutral fragments coincides with that of the unstable intermediates which are suggested in the thermal decomposition mechanism of some related compounds. The loss of C₂H₄ is more characteristic under electron-impact as well as in thermal decomposition of Si-compounds, while C₃H₆ is preferable eliminated by the Ge-compounds.     

Some studies on thallium oxalates. VI

The effect of the thallium(I) concentration on the potentiometric titration of thallium(III) with oxalic acid in 0.1M HNO₃ or 0.05M H₂SO₄ is studied, and conditions are established for the preparation of the thallium(I) bis-oxalato diaquo thallate(III) complex. Chemical analysis of the salt corresponds to the formula T1^I(T1^III(C₂O₄)₂) · 5 H₂O. Thermal decomposition studies on the complex using TG, DTG and DTA techniques indicate the formation of thallium(I) oxalate (stable from 130° to 320°) as the intermediate, the final product being a mixture of thallium(I) oxide and thallium(III) oxide (stable from 520° to 600°). Infrared absorption spectra, X-ray diffraction patterns and microscopic observations are used to characterise the complex and the intermediate.